stormwater introduction bioinfiltration – stephen duda porous concrete – douglas cleary...

Stormwater

• Introduction• Bioinfiltration– Stephen Duda

• Porous Concrete– Douglas Cleary

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Introduction

• Hydrologic Cycle• Watersheds• Implications with Development• Stormwater Management – History– Importance

Hydrologic Cycle

http://ga.water.usgs.gov/edu/watercycle.html

Watersheds

Groundwater Storage

Precipitation

Runoff

Evapotranspiration

Groundwater Withdrawalshttp://science.howstuffworks.com/environmental/conservation/issues/watershed1.htm

Storm Water• Pre development– Trapped in puddles, or– Overland flow impeded by vegetation, and– Infiltration into ground– Plenty of evapotranspiration– Stream Result:

• Post development– Impervious surfaces reduce all of these– Stream Result:• •

Land Use Changes

Image source: Maryland DEP

Flow

Time

Stream Flow

Early Stormwater Management

http://www.acogok.org/Programs_and_services/Water_Resources/Storm_Water.asp

http://www.cityofpa.us/stormwater.htm

• Collect• Convey• Dump

Stormwater Quantity

enviroloknw.com

Stormwater Pollution

http://www.flickr.com/photos/columbiariverkeeper/6153168831/ http://www.niskayuna.org/Public_Documents/NiskayunaNY_DPW/Stormwater

Stormwater PollutantsPollutant Typical Concentration

Total Suspended Solids 80 mg/L

Total Phosphorus 0.30 mg/L

Total Nitrogen 2.0 mg/L

Total Organic Carbon 12.7 mg/L

Cadmium 0.002 mg/L

Copper 0.010 mg/L

Lead 0.018 mg/L

Zinc 0.14 mg/L

Chlorides (winter only) 0.230 mg/L

NJ Stormwater BMP

Stormwater Pollution

Saint Lucie Inlet Floridahttp://www.cityofpsl.com/npdes/

• Stormwater pollution shown on left

What can we do?

• • •

Stormwater Options

• Outdated– Collect, convey, dump in stream

• Traditional– Retention / Detention Pond– Dry Well

• More Recent– Bioinfiltration Basin / Rain Garden– Porous Pavement

Retention Pond

Detention Basin

iowacedarbasin.org

Retention/Detention BasinsTypical Pollutant Removal Rates

Detention Basin

TSS 40 - 60%

Phosphorus 20%

Nitrogen 20%

Retention Basin

TSS 50 – 90%

Phosphorus 50%

Nitrogen 30%

Dry Well

Bioinfiltration Basin

www.geocaching.com

Parking Lotdnr.wi.gov

Wisconsin DNR

www.esc.rutgers.edu

Bioretention Swale

Road-Side

dnr.wi.gov Wisconsin DNR

Under Construction

www.jjaconstruction.com

Plants

Raydons Favorite Aster

Northwind Switchgrass

Seaside Goldenrod

Dark Ponticum Bee Balm

ShenandoahSwitchgrass

Orange Coneflower

Bio-Infiltration Basins

Typical Pollutant Removal Rates

TSS 90%

Phosphorus 60%

Nitrogen 50%

Economicshttp://www.ipa.udel.edu/wra/docs/EconomicValueStormwaterDelawareDraftSummary.pdf

• California: 1,000 trees reduce stormwater runoff by 1M gallons

• Denver: 0.1 ac bioinf basin costs 17% less than traditional retention pond

• Philadelphia: every $1 off green stormwater management saves $2

• Seattle: green stormwater management costs $280,000 per block – versus $425,000 for traditional

Rowan University

Effectiveness

November 8, 2012

First Flush Lysimeter Percent ReductionTSS (mg/L) 37.3 12.7 66%Phosphorus (mg/L) 0.98 0.41 58%Nitrogen (mg/L) 3.00 0.60 80%Zinc (mg/L) 0.06 0.05 17%

Bio-Infiltration Basin Design Basis

• Output = Infiltration through basin bottom– Assume constant rate, as soon as basin begins to fill

• Input = Runoff from contributing area

– Q = P = – Ia = – S =

Q =for P ≤ Ia

for P > Ia

0{ (P – Ia)2

P - Ia + S

More Equations

• Ia = 0.2 S – (Some say more like Ia = 0.05 S)

• S = 1000/CN – 10 – CN = Curve Number• Empirical parameter for predicting runoff or infiltration• Unitless, range: 0 to 100 • Lower number more permeability

[P – 0.2(1000/CN – 10)]2

P + 0.8(1000/CN – 10)Q =

Curve Number Charthttps://engineering.purdue.edu/mapserve/LTHIA7/documentation/scs.htm

Soil Type Infiltration Rate

A > 0.3 in/hr

B 0.30-0.15 in/hr

C 0.15-0.05 in/hr

D 0-0.05 in/hr

• Proper selection of CN is very important!

• More CN tables• Beyond scope of this

course

Equations

• Vr = Q Al

– Vr = Volume of Runoff; Al = Area of Lot;• Ignores ALL rain falling on basin enters basin

• Vi = I T Ab

– Vi = Volume of Infiltration During Storm;I = Infiltration rate; T = Storm Duration, Ab = Area of Basin

• Vb = Volume of Basin = Vr – Vi

• Db = Depth of Basin = Vb / Ab

Bio-Infiltration Basin Example

• Determine bio-infiltration basin depth– 1. Undeveloped, wooded, 1 acre – 2. Residential, Two ½ acre lots

Lot Area

Basin

Given Information

• Lot Area, Al = 1 acre

• Basin Area, Ab = 0.10 acre• Max Basin Depth (must drain in 72 hr)– Infiltration Rate = I = 0.5 in/hr (assumed)– Max Basin Depth = 72 hrs * 0.5 in/hr = 36 inches

• Example Design Storm Hurricane Irene– Precipitation = P = 6 in; Time = T = 18 hr

Bio Basin Example

Undeveloped, Wooded

• Curve Number = CN = 30• Pot. Max. Retention = S = (1000/CN) – 10– S =

• Init. Abstraction– Ia =

•

• Runoff = Q = (P – 0.2S)2/(P + 0.8S)– Q =

– Very low, do not need a basin

Bio Basin Example

Residential, Two ½ acre lots

• Curve Number = CN = 54 • Pot. Max. Retention = S = (1000/CN) – 10– S =

• Init. Abstraction• Ia =

–

• Runoff = Q = (P – 0.2S)2/(P + 0.8S)– Q =

Bio Basin Example

Residential Continued

• Volume of Runoff– Vr =

• Volume of Infiltration– Vi =

• Volume of Basin– Vb =

• Depth of Basin– Db =

• •

Bio Basin Example

Porous Pavers

extension.umd.edu

Porous Pavement

Porous Pavement

upload.wikimedia.org

Concrete• Porous– Cement– Large Aggregate– – Result:

• Normal– Cement– Large Aggregate– Small Aggregate– Result: few voids

archive.inside.iastate.edu

images.huffingtonpost.com

www.lowimpactdevelopment.org

Porous Pavement Storage & Infiltration

www.capecodgroundwater.org

Typical Profile

Porous ConcreteStorage (Typical void space = 15 %)

Subbase – Compacted Stone AggregateStorage

High void space, up to 40 %

Subgrade – Compacted SoilInfiltration

Looking for infiltration rate ~ 0.5 in/hr

Porous Pavement Benefits

• –

• –

• –

•

Passive versus Active• Passive– Only handles rain that

falls on the porous pavement

• Active– Can handle runoff from

surrounding areas

Rainfall Duration

• Design can be based on:– Precipitation during 24 hour period– Precipitation during 2 hour period

• Design storm depends on how often one can accept system overflow– Every two years? Five? Ten?

GlassboroRecurrence Interval, Yr

2 Hour Precipitation, in

24 Hours Precipitation, in

2 1.75 4.2610 2.55 5.0850 3.41 7.39

And storms are getting bigger as a result of climate change

Design Basis

• Permeability of Porous Concrete– Typically NOT an issue: 288 in/hr!

• Storage Capacity– Porous Pavement – Typical is 15 % porosity– Subbase – as high as 40 % porosity (#67, 1” Top Size)

• Infiltration into Subgrade– Typical rule of thumb is the subgrade should infiltrate

~0.5 in/hr• System should drain within 5 days– I’ve seen specifications of 2 – 3 days as well

Active Porous Concrete Example• Given

– Contributing area is as big as porous pavement area• Surrounding contributing area is impervious• What if it was not?

– Porous concrete is 4 in thick with 15 % porosity• Dc = 4 in; Pc = 0.15

– Subbase has 25 % void space• Psb = 0.25

– Subgrade infiltration rate is 0.5 in/hr• I = 0.5 in/hr

– Design for 2 yr storm• T2 = 2 hr; P2 = 1.75 in

• T24 = 24 hr; P24 = 4.26 in

• Calculate depth of subbase

Contributing Area

Porous Concrete Area

APC Example Continued• 2 hr Rainfall– Volume stored in Porous Concrete• Vc =

– Subgrade Infiltration Volume • VI =

– Volume to be stored in Subbase: • Vsb =

– Subbase Depth• Dsb =

Porous Concrete Example

APC Example Continued• 24 hr Rainfall– Volume stored in Porous Concrete

• Vc =

– Subgrade Infiltration Volume • VI =

– Volume to be stored in Subbase: • Vsb =

– Subbase Depth• •

– Subbase depth controlled by 2 hr storm•

Porous Concrete Example

Pavers

www.stonebiltconcepts.com

Eco Pavers

4.bp.blogspot.com static.flickr.com